Techniques for reducing a leakage current from a load have hitherto been proposed. For example, Japanese Patent No. 3044650 and Japanese Patent Application Laid-Open No. 11-122910 (1999) to be described below disclose techniques such that a compensating current supply circuit connected across a smoothing capacitor outputs a current which compensates for a leakage current from a load.
In a structure provided with no smoothing capacitor in Japanese Patent Application Laid-Open No. 2000-92861, a noise reduction circuit is provided between positive and negative input lines providing a connection between a diode bridge serving as a full-wave rectifier circuit and an inverter device. The noise reduction circuit has two transistors which perform the operation of turning on and off.
On the other hand, there are cases where a technique employing a power factor correction circuit is employed as a configuration of a power conversion circuit. In general, the power factor correction circuit is implemented by a boost chopper circuit. For example, when an object that the power conversion circuit drives is an electric motor and the electric motor drives a compressor which compresses a refrigerant for use in an air conditioner, the boost chopper circuit is used from the viewpoint of improving a heating capability at low temperatures.
The boost chopper circuit functionally has a reactor, a switch and a diode. The reactor is provided on the opposite side of the switch from a smoothing circuit.